PM Interval for Power Steering/Air Tank Filters?

You should have a gauge that shows the amount of restrictor pressure being pulled by your filters. After a certain amount of resistance so to speak is reached, you need new filters. Your engine is going through thousands of gallons of fresh air a minute and good clean filters are a must.

I don't know anything about the air tanks on your braking system except that they need draining every night. However your air dryer has that job. Keep a eye on that air dryer to be sure it's doing well and not drowning in algae, water etc.

And the power steering? I had air steering the last truck I drove. I don't know of any steering still running off fluid. But if you are, check it while it's hot now and then. Just like you just came off the interstate into the fueling area.

 

Filters and fluids are cheap insurance that systems will keep functioning normally. Annual service is a good guide for the items you mentioned on the average over the road tractor. Once a year air dryer service and steering system filter and fluid change.